Liquid fuel injection pumps for engines



Sept. 30, 1958 I F. M. EVANS 2,353,947

LIQUID FUEL INJECTION PUMPS FOR ENGINES Filed March 15, 1954 UnitedStates Patent 2,853,947 LIQUID FUEL INJECTION PUMPS FOR ENGINES FraserMackie Evans, Acton, London, England, assignor to C. A. V. Limited,Acton, London, England Application March 15, 1954, Serial No. 416,309

Claims priority, application Great Britain March 16, 1953 1 Claim. (Cl.103-2) This invention relates to liquid fuel injection pumps forinternal combustion engines, the pumps being of the type comprising arotary distributor for connecting the pump successively to the differentcylinders of the engine and also of the type in which no non-returnvalves are provided in the delivery passages.

The object of the invention is to provide in such a pump a simple devicefor relieving residual pressure in the fuel delivery pipes after eachdischarge, the relief being required for the prevention of dribble atthe injection nozzles in the engine cylinders.

The invention comprises a pump of the type aforesaid having in its bodypart adjacent to the rotary distributor, a cylindrical cavity theentrance to which is controlled by the distributor, and a spring loadedplunger in the said cavity, the arrangement being such that at the endof, or shortly before the end of, each discharge stroke of the pump thedistributor establishes communication between the said cavity and thethen associated outlet, so that the residual pressure in the said outletcan be relieved by movement of the plunger, the liquid fuel received bythe cavity being subsequently returned to the pump under the action ofthe spring acting on the plunger.

In the accompanying drawings, Figure 1 is a longitudinal sectionillustrating a pump embodying the invention.

Figure 2 is a cross section on the line 22 of Figure 1.

Figure 2a is a similar view to Figure 2 showing the rotor in a differentangular position.

Figures 3 and 4 are cross sections taken respectively on the lines 3-3and 4-4 of Figure 1.

Figure 5 is a fragmentary View illustrating a modified form of thepressure relief device.

Referring to the drawings, the pump there shown comprises a body part awhich contains a rotor b. On the rotor is formed an enlargement c whichserves as the pump barrel. One end of the rotor extends beyond the bodypart and receives motion from any convenient source. The other end ofthe rotor serves as the distributor.

In the part c is formed a diametrically disposed bore d which containstwo pump plungers e, and in the body part is included a cam ring 7 withwhich the outer ends of the plungers co-operate.

In the distributor are formed an axial bore g which extends from thecentre of the bore d, four radial fuel inlet ports 11 which communicatein turn with a single fuel inlet i in the body part, and a single radialoutlet port j which communicates with each in turn of four fuel outletsk.

The arrangement is such that rotation of the rotor Patented Sept. 30,1958 causes fuel to be intermittently drawn into the space between theadjacent ends of the plungers e and subsequently discharged in turnthrough the outlets k to the associated injection nozzles (not shown).

According to the invention there is provided in the body part a and inthe plane of the ports h, a small lateral cavity 0 which is open at itsinner end and which contains a plunger m. At the end of the plungerremote from the open end of the cavity is formed a head 12 which iscontained in a larger part of the cavity, the

latter containing a weak spring p which holds'the plunger in its normalposition. The cavity 0 is provided with a vent q.

The arrangement is such that at or near the end of each discharge actionof the pump the open end of the cavity 0 is put into communication withan adjacent closed inlet port h, thence through the bore g and port jwith the discharge passage k through which liquid fuel is then beingdischarged to the engine. The effect of this condition, which isillustrated in Figure 2a, is to enable the residual pressure in thedischarge pipe communicating with the cavity to be relieved by movementof the plunger in under the action of this pressure and against theaction of the spring p acting on the plunger. In this respect it will beunderstood that as communication between the cavity 0 and one of theinlet ports h is established before communication between the port j andany one of the discharge passages k is interrupted, and as the spring pacting on the plunger m in the cavity is weak, the residual pressure inthe discharge passage communicating with the cavity will, as a result ofthe movement of the plunger against the action of its loading spring, bereduced sufliciently to prevent dribble at the associated injectionnozzle. Later the cavity is isolated by a plain unported peripheralportion of the distributor, and during the next suction action of thepump this liquid is returned through the distributor to the pump by thepressure of the spring on the plunger.

To enable the amount of liquid accommodated in the relief cavity to bevaried, there is provided an adjustable stop r as shown in Figure 5.This stop r is arranged in screw-thread connection with the body part sothat by actuation of an external lever s the position of the inner endof the stop can be adjusted for varying the range of free movement ofthe plunger m. This adjustment is also useful in enabling an additionalamount of fuel to be supplied to the engine when starting.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

A liquid fuel injection pump comprising in combination a hollow bodyprovided with a fuel inlet, a plurality of fuel outlets, and acylindrical cavity open at one end to the interior of the body, aspring-loaded plunger in the cavity, and a rotary distributor mounted inthe body, and having therein a pumping chamber, an axial passageway openat one end to the pumping chamber, another passageway extending betweenthe axial passageway and the outer periphery of the distributor in aplane containing the'fuel outlets of the body, and additionalpassageways extending between the axial passageway and the outerperiphery of the distributor in another plane containing the fuel inletand the cylindrical cavity of the body, whereby, during rotation of thedistributor. communication is intermittently established between thefuel inlet and the pumping chamber, between the pumping chamber and eachfuel outlet in turn,

and between the cylindrical cavity and both the pumping chamber and eachfuel outlet in turn, the cavity being arranged so that communicationthereof with the pumping chamber and each fuel outlet in turn isestablished through the associated passageways in the distributorpreparatory to isolation of each fuel outlet from the pumping chamber bythe distributor, thereby enabling residual pressure at each fuel outletto be relieved by liquid fuel flow from the distributor into the cavityagainst the action References Cited in the file of this patent of thespring-loaded plunger which subsequently returns 10 2,730,173

the liquid fuel from the cavity to the distributor.

UNITED STATES PATENTS Varley Sept. 18, 1934 Kamrner Dec. 9, 1941 GallSept. 17, 1946 Drouot Jan. 15, 1952 Evans et a1. June 2, 1953 Evans Nov.3, 1953 Herbrich Feb. 5, 1957

